Explosively operated industrial tools utilizing cartridges having explosive powder and a primer for detonating the powder are disclosed in U.S. Pat. Nos. 3,007,409 and 3,155,039. Both of these patents disclose cartridges that include a gas check member that has one end adjacent the explosive powder and the other end facing outwardly with a detonator primer therein. An opening communicates between the primer and the explosive powder. A ram is arranged so that it can be made to slide into the open end of the cartridge, strike the primer, thereby igniting the explosive powder which then forces the ram outwardly to perform the desired work operation. The tool includes a piercer pin that pierces through the shell casing and into the chamber holding the explosive powder. After ignition, the gases from the explosion are trapped within the cartridge because the gas check remains within the open end of the cartridge blocking possible escape. To release these trapped gases the piercer pin is moved away from the cartridge a small amount, thereby allowing the gases to escape through the pierced opening in the shell casing. When the tool has been in use for a long time, the piercer pin may become worn, broken, or otherwise damaged and may not pierce completely through the shell casing. When this occurs the cartridge may remain under pressure after it is removed from the tool.
What is needed is a cartridge that automatically undergoes a controlled fracture during ignition only when the piercer pin is badly damaged so that the gases can escape through the fracture by the broken piercer pin. However, the cartridge must retain the gases when the piercer pin is normal and has completely pierced through the shell casing.